Devices of this type are sunk into the refractory cladding of a metallurgical container, generally in the bottom, for the purpose of proceeding with the treatment of the molten metal contained therein, by input of electrical energy. Such devices hence constitute electrodes connected at one end to a charged electrical source and in contact at the other end with a metallic bath, thereby assuring the passage of electric current to the bath.
Among metallurgical containers which may be equipped with such electrodes are electrolytic metallurgical vats for non-ferrous metals, such as aluminum, or in the metallurgy of iron and steel, ladles for treatment and temperature maintenance, or electric melting furnaces, particularly direct current arc furnaces capable of accepting electrical strengths in excess of 30,000 amperes without damage to the electrode.
One of the essential problems encountered by prior art devices is the behavior over time of the electrode whose terminal portion, in direct contact with the molten metallic mass, is subjected, in addition to the above-mentioned joule effect, to very severe thermic stresses due to the very high temperatures which, especially in the case of molten steel, can reach 1800.degree. C. or even more.
Various methods of assuring satisfactory cooling of the electrode are known.
In a first group of such methods, cooling fluid is brought to the immediate vicinity of the hot end of the electrode. However, even a reduced degree of melting of the electrode involves the risk of destroying the cooling system, and hence a dangerous contact of the fluid with the liquid metal.
Another group of solutions, to which the present invention belongs, involves a cooling system external the electrode, located outside the metallurgical container. French Pat. Nos. 1,538,996 and 2,292,367 may be cited in this connection. While being safer, such solutions are not really satisfactory. The distance between the hot end of the electrode and its cooled end which passes to the exterior of the bottom of the container may be the cause of the final disappearance, through melting, of an excessive portion of the electrode, thereby compromising to a dangerous extent the leak-tightness of the container with regard to the molten mass which it contains.